Knurling device



A ril 14, 1953 c. .F. JONES KNURLING DEVICE 3 Sheets-Sheet 1 Filed June 11, 1942' INVENTOR. -Ce7'7 gwZ 1f0nea BY 3 C. F. JONES KNURLING DEVICE April 14, 1953 3 Sheets-Sheet 2 Filed June 1]., 1949 QQN 3% 8 m6 m6 .1 N ww PM: mm 9 mW w Q n? Ill |I||| .l. %W q Qu hN w% ww NM. E m5 l l l l I...

mm T w Nu v M J, 1: m, mm m; t; U/QQ L Q \N\\ \NN mww \wNN @NI mN QNNNN MN April 14, 1953 c. F. JONES KNURLING DEVICE 3 Sheets-Sheet 5 Filed June 11, 1949 Patented Apr. 14, 1953 KNURLING DEVICE Cernyw F. Jones, Economy, Ind., assignor to Perfect Circle Corporation, Hagerstown, Ind., a corporation of Indiana Application June 11, 1949, Serial No. 98,599

12 Claims.

This invention relates generally to a knurling device for knurling the peripheral surface of a cylindrical object and more particularly to a device for knurling predetermined areas on the peripheral surface of a hollow cylindrical article such. as a piston for an internal combustion engine.

With continued operation of an internal combustion engine, the pistons and cylinders tend to wear or become distorted with the result that the normal fit of the pistons within the cylinders is lost. This condition is often characterized by piston slap and other evidence of excessive looseness. The lack of proper fit between the piston and the cylinder is objectionable since it impairs engine efficiency and has an adverse effect on the economy of operation.

Various means for correcting this condition have been employed, one method involving the expansion of the outer wall or skirt portion of the piston sufficiently to reestablish the normal fit between piston and cylinder. Such expansion may be accomplished, for example, by knurling the outer surface of the piston to form roughened areas on the thrust faces thereof having an interrupted surface comprising projecting portions with intervening depressions. During knurling the metal is extruded or swaged to a sufiicient extent so that the projections formed on the pis' ton surface extend outwardly to the desired increased size whereby the proper fit between the piston and the cylinder is realized.

. Although during knurling of a piston the work may be supported or stabilized by hand of the operator, it is generally desirable. to provide the knurling device with a suitable work-supporting member or structure which results in more efiective stabilization of the piston during knurling and also frees both hands of the operator for manipulation of the knurling mechanism proper. Because the normal contour of a piston is slightly oval or out-of-round, it is necessary that such a work support be designed to permit a limited degree of relative movement between the piston and the knurling mechanism in order tocompensate for the varying piston diameter. In addition, the knurling mechanism preferably comprises an anvil member or other supporting means adapted to engage and support the piston internally while a knurling element engages the exterior of the piston under pressure. However, the interior surface of the skirt portion of a piston is usually quite uneven in the area between the wrist pin bosses because of various protuberances and surface irregularities such as, reinforcing ribs, partial machining of the interior surface, and general surface roughness characteristic of cast articles. Thus, the problem is presented of providing a knurlingv device which will readily accommodate the variations in piston wall thickness while at the same time avoiding any substantial change in knurling pressure against the outer surface of the piston.

Accordingly, one object of my invention is to provide a device for knurling the exterior surfaces of pistons which readily accommodates variations in piston wall thickness while maintaining a substantially constant knurling pressure.

Another object of my invention is to provide a device for knurling the exterior surfaces of pistons in which a supporting member engages the interior of the piston, a knurling member engages the exterior of the piston, and the spacing between said members is permitted to vary automatically to accommodate protuberances and other irregularities on the interior surface of the piston.

An additional object of the invention is to provide a simple hand-operated device for knurling the exterior surfaces of pistons in combination with a novel work support adapted to stabilize the piston in both horizontal and vertical planes during knurling.

A further object of the invention is to provide a device for knurling the exterior surfaces of pistons, said device having manually operable means for adjustably spacing the knurled areas axially of the piston.

Other objects and advantages of the invention will become apparent from the subsequent detailed description of the invention and the accompanying drawings, in which:

Fig. 1 is a front elevational view of a knurlin device comprising one specific embodiment of my invention;

Fig. 2 is a fragmentary top plan View of the device shown in Fig. 1;

Fig. 3 is a fragmentary vertical sectional view taken. along the line 3--3 of Fig. l;

v Fig. 4 is an end view of the device when viewed from the left in Fig. 1; and

Fig. 5 is an end view of the device when viewed from the right in Fig. 1 with portions thereof in section.

As heretofore mentioned, the knurling device comprising the present invention is provided with a pair of cooperating anvil and knurling elements, the anvil element being arranged to support the piston internally while the knurling element bears against the outer surface of the piston. The knurling element is preferably in the form of a small roller which is applied to the outer surface of the piston in rolling relation therewith so that the resultant area knurled in one application of the tool comprises a band having a width equal to the width of the roller. Usually the roller is relatively narrow and traverses the piston circumferentially so that a plurality of such knurled bands are required to cover a desired area longitudinally of the piston. The knurled bands may, of course, be disposed in continuous abutting relation to one another or they may be slightly spaced from each other longitudinally of the piston.

With a piston for an internal combustion engine, it is necessary to knurl only the thrust faces of the piston skirt, i. e. those portions which are subjected to lateral thrust against the cylinder wall due to the position of the connecting rod. Thus, the knurling operation may be restricted to the portions of the piston skirt lying intermediate the wrist-pin holes on opposite sides of the piston. The knurled area preferably starts immediately below the ring grooves at the upper end of the piston and may extend axially or longitudinally for the full length of the piston skirt. treme outer end of the skirt may be spaced differently from the remaining bands in order to position the outermost band as close as possible to the edge of the piston.

In addition to effecting expansion of the piston metal by extrusion thereof, in the manner hereinbefore described, whereby to reestablish a proper fit between the piston and the cylinder, the knurled surface obtained by my invention also offers other important advantages. For example, it has been found that better performance is obtained in a reciprocating piston and cylinder, or other like construction, if one of the two surfaces is of an interrupted nature comprising projecting portions with intervening depressions, such as may be provided by knurling. A surface of this character has been found to run cooler than an absolutely smooth surface for pistons as well as other cylindrical objects adapted to reciprocate within a bore. Another advantage inherent in knurling the surfaces of pistons and like articles is found in the improved wearing qualities of the knurled surface resulting from the hardening effects of cold working the metal.

In addition, the interrupted surface afforded by knurling provides a series of pockets or reservoirs which serve to retain lubricating oil and thereby maintain a continuous supply of lubricant at the surface contacting areas.

a It will be apparent that, in addition to the obvious utility of knurling old or worn pistons in order to expand the same, knurling may also be resorted to in the case of new pistons or original assemblies of pistons within their cylinders in order to attain the other advantages mentioned above. While the knurling device comprising the present invention is designed primarily for knurling pistons, the invention is not limited in this manner but embraces the knurling of the peripheral surfaces of hollow cylindrical articles generally.

The term knurling as used throughout the specification and the claims is not limited to the ordinary form of knurling involving grooves ar ranged in a criss-cross pattern, but rather is used in a broad sense to include any surface formation involving alternate depressed and raised portions regardless of whether one or the other or both of said portions are continuous throughout the area having such formation.

If desired, the knurled band at the exa 4 Thus, the term includes not only the cries-cross pattern but also a pattern formed by parallel grooves or by isolated indentations resulting in connected raised portions.

As hereinbefore mentioned, an important object of my invention is to provide a knurling device for pistons which is designed to accommodate varying piston wall thicknesses due to internal protuberances or surface irregularities while at the same time avoiding substantial changes in knurling pressure and eliminating the need for manually adjusting or regulating the device during a-knurling operation. I accomplish this end broadly by providing a rigidly mounted knurling member and a cooperating anvil member connected for pivotal movement toward and away from the knurling member, in combination with a spring means for yieldingly urging the anvil member toward the knurling member. The yieldable urging of the one member toward the other permits a variation in spacing between the members upon contact of the anvil member with protuberances on the interior surface of the piston skirt while the knurling member bears with substantially constant pressure against the exterior surface of the skirt.

Referring now to the drawings, which show by way of illustration one specific embodiment of my invention, the device is provided with a rectangular base 25 having at each of its opposite ends a pair of apertured lugs 26 for screwing or bolting the device to a bench surface or other suitable support. Extending upwardly at one end of the base 25 is a work-supporting structure, indicated generally at 21, which comprises an upright post 28 rigidly fastened to the base at the rear thereof, as by means of a plurality of screws 29 (Fig. 4). A pair of upper and lower stabilizing arms, 3! and 32, respectively, project forwardly from the post 28 and are adapted to receive a, piston 33 diametrically therebetween and to support the same longitudinally above the base 25, as described hereinafter in detail.

For supporting the knurling mechanism proper, a carriage 34 is slidably mounted on the base 25 and is operatively connected thereto, by means hereinafter described in greater detail, for movement longitudinally of the piston 33 toward and away from the Work supporting structure 27. At one end of the carriage 34 nearest the post 28 is an upright knurl support in the form of a bracket 36 having a knurling roller 31 journaled at the upper end thereof. The roller 31 is rotatably mounted on the bracket 36 by means of a pair of bearing s1eeves'38 (Fig. 1) keyed to the roller 31, the bearing sleeves 38 and the knurling roller 31 being clamped together and secured to the end of a drive shaft 39 by means of a'stud 4| extending longitudinally through the sleeves and the roller and threaded into the end of the shaft 39. A nut 42 is secured at the outer end of the stud 4| for retaining the sleeves 38 and the roller 31 in clamped relation. The drive shaft 39 extends longitudinally of the carriage 34 and is journaled and supported at its opposite endby a bearing bracket 43 extending upwardly at the other end of the carriage 34 remote from the post 28. The bearing bracket 43 is rigidly fastened to the carriage 34 by means of a pair of screws 44,. A hand crank 35 extends through an aperture adjacent the end of the drive shaft 38 for manually driving the knurling roller 31 and is adjustably secured thereto by means of a set screw 41. I

To provide an anvil support, an upright slightly n enrvedrlever or bracket 48 .is .rastened at its lower 'end'to :a pivot .shait 19 by means-rot ascrew 51, the shaft 49 ioeing j omna'led in an integral hear" ing portion .52 :at therear of the carriage 34 and extending longitudinally thereof. An elongated anvil-supporting arm 53 extends later-ally from the upper end :of the bracket "48 in a 'direcidon generally parallel to the drive shaft .33, the :arm '53 bemgiastened to the upper end of the bracket 48 by :meansof a :of screws :54 -(Fig. 2 The outermost end of the arm 53 is provided with a pair of spaced projections between which is mounted for free rolling movement an anvil member in the form :of :a hard smooth surfaced roller 56 having approximately the same diameter and width as the knurling roller .31 The .anvil roller 56 rotates on :a shaft or pix-1:51 and is urged outwardly of the arm 5.3 :by :means of a coil spring v58 encircling the :pin 5] whereby the anvil roller 56 is normally maintained in radial alignment with respect to th .knurlin-g roller 3-] but :can Joe displaced axially thereof in the event that the anvil roller encounters an internal ridge or other :circumferential projection I on the interior of the piston.

Itwill beseen that by rotary 'or rocking move- .ment :of the pivot shaft 49 carrying the upright bracket 48, the arm 53 and the anvil roller 5% carried thereon may be moved away from and toward the knurling :rollerfll. During aJknu-rling -i-i operation, the skirt portion of the piston .33 is clamped between the two rollers, the anvil roller '56 being disposed against the interior surface of the piston skirt and the fknurling roller 31 bearing against the outer periphery of the piston skirt with the axes of the rollers being parallel to the axis of the piston. As the knurling roller 3-! is driven by operation of the hand crank 46, the piston 33 also rotates about axis "rolling relation toithe roller 3?! which is in tight engagementtherewith.

The gpivot sha'f t 4.9 is provided with an end portion :59 of reduced diameter (Fig. 1) which extends from the end of .the bearing portion 52 adjacent the bracket 36. For :49, a relatively short lever ii] is provided in the .form of a "U shaped member having a base portion 62 "and a pair of upright spaced arms indicated :at 63.. The base portion 2 of the lever 51 is rigidly secured to the projecting endnortion 59 of the shaft 49 ior rotation therewith and a swivel or rotatable pinfie extends between the-upper ends-of thearms 63.

.A horizontally disposed :spring loading device.

indicated generally at 6'6, .coacts with the swivel l 54 .ior applying adjustable yielding pressure against the lever :61 in order to urge the anvil :roller 56 toward the knurling roller 31 by :rock ing movement of the pivot shaft 49 and the bracket 48 carried thereon. elongated stud 16-! having terminally threaded portions extends longitudinally between the zarms-53 of the lever 5] and through a transverse aperture 58 in the swivel to (Fig, 73). Ascrew 59 0f larger diameter than the stud 6-1 and having a manually operable :head portion 7H, :extends irom the front of the device through :an enlarged :concentric bore 12 in the bracket .35 and is threaded in :a swivel 1.3 which is in the form of ashaftrotatablysupported in the bracket 3-6 transversely of the bore :12. The forward end of the stud 5:1 is tightly connected to the inner endo'f the "screw 59, as by'an internally threaded axial bore .14 in the screw 69 which receives the threaded end of the stud 61. Thus, the screw rocking the shaft To this end, i:

as is in effect integral with/the stud ca. use

.screw .69 being :of larger diameter than the stud -61, the annular end face 50f thescrew =69 .zatgits juncture with the stud v6.! forms a shoulder,- :as indicated at 1.6, which adapted to :coact a flattened recess 1.! cutout of the periphery of theswivel "64 opposite the shoulder 1-5.

.Encircling the stud .67 .is a "helical spring '18 adapted to apply yielding pressure against the swivel 64 through a thrustcollar comprising ;a

sleeve 19 carried on the stud .6?! and having a flanged end 8:! bearing against one end of the spring .18.. .Thezfiange .8! is ,adaptedrto operatively engage the swivel $54 and .for this nurpose iszrespring 1-8 through a thrust bearing .84 and a thrust collar comprising a sleeve BB having afianged end 81, similar to the sleeve :19 and fiangefll.

By adjusting the nut .83., the tension or the spring 18 can be regulated to control the pressure exerted on the :lever 61 through the vswivel '64 and thereby regulating the knurling pressure, e. the pressure under which the skirtportion :of the piston 33 is pressed againsttheknurling roller *31 by means of the :internal anvil roller 56. A ,jam or look :nut =88 .is carried on the stud 61 adj acent the adjusting .nut 8.8 :forilocking the latter inplace after vthetensionoi spring '!8 has been adjusted to any desiredextent.

The operation of the spring loading device'fifi is as follows: .In the position shown in Figs. and 5, the screw 6.9 has been screwed outwardly through its threaded connection with the swivel 1.3 a sufficient distance so that a slight clearance,- indicated at 8:9 in :Fig. 3, is established between the shoulder 1:6 at the inner end of the :screwid and the recess 'l the swivel 4. Thus, the full pressure of the spring I8 is brought to bear on the shaft 64 thereby urging the lever 6| Pin a counterclockwise direction, as viewed in Figs. 3 and 5, and urging'theshaft .49 and the bracket 48 in :a similar direction whereby'they-anvil roller 55 is goressed toward the lmurli-ng roller 31 with the skirt portion of the piston -33 being clamped therebetween. As described above, the :knurling .pressure :may be controlled by adjusting the nut 83 to regulate the tensionoi thespring 118.. I o

.By means of the operating head '1] .on the screw 69 at the front of the device, the screw .69 may be screwed inwardly through the swivel- ?!3 until the shoulder '16 abuts the recess 11 in the swivel :64 thereby rendering the spring load inefiective when the clearance 9 is taken up. At this point, continued inward movement the screw -69 causes the lever ii to be rocked in a clockwise direction, as viewed in Figs. '3 and 5., and the anvil roller 56 is thereby 'IdLlS-. engaged from the interior surface of the skirt portion of the piston 3-3 as the bracket 48 rocks in a similar direction with the :pi-vot shalt 4:9. With the rollers .33! and 5.6 in radially spaced position, the carriage 34 may be moved axially of the piston .33, by means hereinafter describedin detail, to position the sknurling mechanism at any desired location longitudinally of the As the lever 6| swings in an arcuate path during movement of the anvil roller .56 to released position, the rear end of the stud 6] r and its integrally connected screw 69 pivot 'dn'wnwardly slight, as viewed in Figs. 3 and 5,

in the plane of the bracket 36. To accommodate this pivotal movement of the stud 6'! and the screw 69, the swivel I3 and the swivel 64 rotate freely in their respective supporting structures, the bifurcated relation of the arms 63 on the lever BI and the enlarged bore I2 in the bracket 36 providing sufficient clearance to permit the stud 61 and the screw 69 to assume the necessary angular position.

During the inward movement of the screw 69 as described above, the tension setting of the spring 78 is not disturbed materially since the spring tension is determined by the relative position of the adjusting nut 83 on the stud 61. Inward movement of the screw 69 from the position shown in Figs. 3 and 5 until the clearance 89 is taken up will result in a very slight decrease in the spring tension setting, equivalent to the extent of the clearance 89, but this change is of no practical consequence. Thus, it will be seen that the'anvil roller 56 can be backed away from the interior of the piston 33 without unloading the spring I8 or otherwise changing the spring tension setting.

' To return the device to knurling position, the screw 63 is operated in-reverse fashion whereby to move the same forwardly of the device and of the swivel I3. The tension of the spring 73 acting on the swivel 64 pivots the lever 6i and its associated shaft 49 and bracket 48 whereby to swing the anvil roller 56 into contact with the inner surface of the skirt portion of the piston 33. Upon continued backing away of the screw 69, the. shoulder I6 is disengaged from the recess 17 and the roller 56 is urged against the piston 33 with sufficient pressure to sink the ridges on the knurling roller 31 into the outer surface of the skirt. Further movement of the bracket 48 and lever BI is prevented, and forward movement of the screw 69 is then continued until the slight clearance 69 is reestablished between the recess 1'! and the shoulder 16. Thus, the spring I8 is returned substantially to its original tension and the full spring load is again imposed on the swivel 64. Once the clearance 89 is obtained, further operation of the screw 59 is unnecessary since the establishment of the slightest clearance at this point permits the full spring tension, as determined by the setting of the nut 83, to be applied against the "swivel 64',

As' hereinbefore mentioned, the carriage 34 is movable relative to the base and longitudinally of the piston 33 in order to provide the latter with a plurality of axially spaced knurled bands or tracks while the piston 33 is held longitudinally above the base 25 by the work-supporting structure 21. For effecting movement of the carriage 34 along the base 25 away from and toward the work-support 21, a rack 90 is mounted on the base, with its teeth extending upwardly therefrom and is slidably received within an elongated groove or slideway 9I (Figs. 4 and 5) at the under side of the carriage 34. The rack 90 thus functions as a guide for the carriage as the latter travels on the base 25. The carriage 34 is provided with a re'arwardly extending boss 92 (Fig. 2) having a pinion shaft 93 (Fig. 5) journaled therein and carrying a pinion 94 at its inner end for engaging or meshing with the teeth of the rack 90. A hand wheel 96 is secured to an extension 9'! of reduced diameter at the front end of the pinion shaft 93 for rotating the pinion 94 and thereby effecting movement of the carriage 34 in either direction relative to the rack 90. A retaining collar or yoke 98 is disposed around the extension 91 between the hand wheel 96 and the pinion shaft 93 and is fastened to the boss 92 by means of a screw 99.

In order to clamp the carriage 34 in place at any desired position relative to the rack 90, a stud IOI (Fig. 1) depends from an ear I02 on the carriage 3'4 and extends through an elongated slot I03 (Fig. 5) in the base 25 parallel to the rack 90. A clamping nut I04 is threaded to the lower end of the stud I M at the under side of the base 25 and. is provided with a handle I06 extending'forwardly beyond the base. In order to hold the carriage 34' insnug but movable relation with the base 25 when the clamping nut I04 is loosened preparatory to effecting travel of the carriage 34, a retaining washer I0! is disposed on the stud IOI between the clamping nut I04 and the under side of the base 25 and a helical spring I08 (Fig. 1) is provided in an internal recess I09 in the nut I04 for exerting pressure between the clamping n'ut I04 and the washer I01. During a knurling operation the peripheral surface of the piston 33 is held squarely against the face of the knurling roller 31 by means of the clamping action of the anvil roller 56 forcing'the piston skirt against the knurling roller. However, an important feature of my invention is the work-supporting structure 21, hereinbefore briefly described, which stabilizes and supportsthe piston 33 in a vertical direction during knurling. The piston 33 is retained'with its axis horizontal above the base 25 between the stabilizing arms 3| and 32 which extend forwardly from the post 28 and are vertically spaced from each other substantially the diameter of the piston. The lower stabilizing arm 32- is adjustably mounted on the post 28 by means of a socket portion I10 in slidable engagement with the post 20; For holding the arm 32 squarely and rigidly on the post 28. an elongated key III (Fig. l) fits into a longitudinal groove or keyway H2 in the side" of the post 28 and extends into a complementary groove or keyway II 2' in the socket II 0. A clamping screw H3 extends through one side of the socket IIO and engages a cone socket, indicated at 3', provided in the key III for securing the arm 32 at any desired elevation above the base 25.

Because of the normal oval or out-of-roun'd contour of a piston, the upper stabilizing arm 3I', while adapted to be generally fixed relative to the post 28, is also flexibly 0r resiliently mounted in order to accommodate the varying piston diameter as the piston 33 rotates on its axis between the arms 3| and 32 upon driving of the knurling roller 37. In order to provide this ee sired flexibility or relative movement between the arms 3| and 32, the upper stabilizing 'arm'3I is movably mounted on the post 28 and having an internal diameter slightly greater than the diameter of the post 28 in order to provide a slight clearance or loose fit therebetween. A clamping screw II5 extends through the side of the socket I I 4 and is provided at its inner end with a conical point (Figs. 1 and 2) for engaging a key II6 fitting snugly in the groove I I2. A complementary pivot member in the form of a conically pointed set screw II8 extends through the socket I I4 opposite the screw I I 6 and engages a key I II fitting snugly in an elongated groove II9, similar'to the groove II 2, on the opposite side of the post 28'. The socket portion H4 is provided with corresponding keyways to receive the keys H6 and H lbut these keyways' are slightly wider than the keys. A helical spring iii (Fig. 4) is disposed in a bore 5-22 in the arm 3% at the inner end thereof adjacent the socket I it and bears against the post 28' above the pivot screws H6 and H8 whereby to urge the arm 31 downwardly as a result of the pivotal connection of the latter with the post 28. Thus, the arm 31 may be positioned on the post 28 at any desired spacing above the arm 32, dependent upon the-size of the-piston being knurled, while at the same time, because of the clearance between the post 28' and the socket portion HQ and because the keyways in the socket portion I M are slightly wider than the keys H8 and ill, the pivot screws H6 and H3 permit limited pivotal movement of the arm 3! relative to the post 28.

Because of the spring-pressed relation of the arm 3i against the exterior of the piston the arm- 3i may" pivot upwardly and downwardly relative to the arm 32' as the effective diameter of the piston 33 varies slightly during rotation of the latter about its axis. Thus, it will be seen that the work-supporting structure 2? of my device effectively stabilizes the piston 33 in a vertical direction while at the same time permitting the necessary degree of movement of the piston because of its'oval' form. In addition, the springpressed' relation of the arm 31 against the piston 33- also permits the piston to rotate freely during knurling and to slide horizontally between the two stabilizing arms as the anvil roller 56 is swung into engagement with the interior of the piston skirt and presses the latter against the knurling roller 31" at the beginning of a knurling operation.

A key in the form of a relatively thin plate [23 is fastened adjacent the bottom edge of the arm 3 I by means of aplurality of screws 124'. As best seen in Fig; 1, the key #23 extends below the arm- 3| and. is adapted to be received within one of the piston. grooves in order to prevent any tendency toward endwise movement or longitudinal displacement. of the piston 33 during operation of the device;

In knurling a piston with the device shown in the drawings, the piston 33 is first mounted in clamped relation between the stabilizingv arms 3 l and 32'. of the work-supporting structure 2! with the key I23 being received in one of the ring grooves of the. piston in order" to prevent endwise movement of the piston during knurling'. During the mounting of the piston in the work'- supporting structure 21', the carriage 3 3, having the knurling mechanism proper mounted thereon, is positioned at the far end of the base 25 free of the skirt portion of the piston. The elevation of the piston 33' with respect to the base 25 is ad justed so that the axis of the piston is in substantially the same horizontal plane as the axes of the knurling roller 3? and the anvil roller 56. The horizontal position of the piston 33 relative to the post 28- is also adjusted by sliding the piston between the arms 3! and 32' away from or toward the post2-8 as required so that the skirt portion of the piston will olear'theknurling roller 37 to permit thel'atter to engage the outer periphery of the skirt.

With the bracket 48 in released position sotha-t the rollers 3-1 and 56 are in spaced relation, the hand wheel 96 is actuated to effect movement of the carriage 34 toward the open end of the piston. During travel of the carriage, the clamplug nut IE4 is, of course, loosened slightly and the spring-loaded washer H11 maintains the car'- riage 34 snugly againstthe base 25 while at the same time permitting sliding movement thereof. The carriage 34- is moved toward the piston 33 until theskirt: extends between the rollers a'i' and 56 to the desired extent, and at this point the carriage 34' is clamped securely in. place on the base 25 by tightening the clamping nut Hit. Upon adjustment of the nut to obtain the desired tension in the spring K 3 and upon backing away of the screw 59 to return the. bracket 48 to operating position, the desired knurling operation may then be carried out. by rotating the hand crank' 46 which. drives the knurling roller 31.

Rotation of the hand cranku tt results. in. relative rolling movement between the knurling roller 31 and the piston 33 circumferentially 0f the latter. Because the skirt. portion of the piston 33 is clamped between the rollers 3.1. and. 56,. rotation of. the knuriing roller 3! also causes simultaneous. rotation. of the. piston about its axis whereby to. formv an arcuate knurled. band on the. outer periphery of the skirt, as hereinbefore described. As a. result: of. thepivoted mounting of the upper stabilizing. arm 31 on the post. 28 and the spring-pressed relation thereof with respect to the piston 33, the. arm. El. pivots up. and down as. it. rides. on. the periphery of the. piston and thereby accommodates the variations in. piston diameter: as the latter rotates between the arms 31 and. 32.. During knurling the piston is stabilized in all. directions by the. clamping. action of the rollers 58 and. 31,.by the clamping action of. the arms-.31 and 32, and by'theretaining. action of: the key 123.

During the. course of a. knurl'ing operationif the: anvil roller: 5.6 encounters internal protuberances or' other surface. irregularities on the interior of the piston. skirt, it. will be. seen. that the yielding applicationv of the anvil roller 56, by the spring loading. device 66, against the: inner surface of the. piston skirt permits the roller; 56 to be forced away from the protuberance, the bracket. 48. rocking in a. clockwise direction (as viewed. in. Figs. 3 and 5): along. with the pivot shaft 49: and. the: lever: (it. The slight. compression of thelspring 18 resulting fromv suchv rocking movement as the. lever Bl isforced rearwardly of the device; against the action of the spring 18 will have no significant: effect on the pressure with which the skirt portion of. the pistonv 33 is clamped between the rollersal and 56. Thus, my device. provides for substantially constantv knurling' pressure, as predetermined: by the setting of the adjusting nut- 83 and the lock nut 88, even when the radial spacingbetween the rollers 371 and 56 varies as the anvil roller 56 passes over surface. irregularities on the interior of the. piston skirt.

As'hereinbefore mentioned, the diameters and Widths of the knurling roller 31- and the anvil roller 56 are preferably substantially the same. Such a relationship insures that the anvil roller will havean area of engagement with the interior of the piston skirt which lies substantially within the area of engagement of the knurling roller with the exterior of the skirt, thereby avoiding any possibility of undesired peripheral distortion of the piston skirt as a result of the pressure be-- tween the knurling and anvil rollers. Of course, theswaging action of the knurling roller results in an increase in the diameter of the piston skirt, as hereinbefore described.

' Although the invention has been described in detail with reference to one specific structural 1 l embodiment, it will be understood'that various modifications and equivalent structures may be resorted to without departing from the scope of the invention as defined in the appended claims.

I claim:

1. Knurling means for a device for knurling The thrust faces of the skirt portion of a piston, comprising a base, a carriage slidably mounted on said base for movement longitudinally of the piston, knurling mechanism supported on said carriage and comprising a knurling roller adapted to engage the exterior surface of the piston skirt and an anvil member adapted to support the skirt interiorly thereof, and actuating means for effecting travel of said carriage along said base, said actuating means comprising a rack mounted on the upper surface of said base and the under side of said carriage having a groove in which the rack is slidably received whereby to guide the travel of said carriage on said base, and a manually operable pinion mounted on said carriage and meshing with said rack.

. 2. Knurling means for a device for knurling the thrust faces of the skirt portion of a piston, comprising a base having an elongated rack at the upper surface thereof and an elongated slot parallel to said rack, a carriage slidably disposed on said base for movement longitudinally of the piston, knurling mechanism mounted on said carriage and comprising a knurling roller adapted to engage the exterior surface of the piston skirt and an anvil member for engaging the skirt interiorly thereof, a manually operable pinion journaled in said carriage in operative engagement with said rack, a stud extending downwardly from said carriage through said slot, a clamping nut threaded on the lower end of said stud for clamping said carriage to said base, and a spring coacting between said nut and the under side of said base for retaining said carriage in movable engagement with said base when said clamping nut is loosened to permittravel of said carriage.

, 3. A device for knurling the thrust faces of the skirt portion of a piston of slightly oval shape, comprising a base, a work support on said base for holding a piston thereabove during knurling and for stabilizing the piston during rotation thereof on its axis, and knurling mechanism slidably mounted relative to said base for movement away from and toward said work support longitudinally of the piston and comprising a pair of members adapted to clamp the wall of the piston therebetween with one of said members being rotatable to rotate the skirt of the piston therebetween, said work support comprising an upright post at one end of said base and a pair of upper and lower stabilizing arms mounted on said post for vertical adjustment and extending outwardly therefrom for receiving the head end of the piston diametrically therebetween, one of said arms being mounted for limited pivotal movement relative to said post whereby to accommodate the varying diameter due to the oval shape of the pistonvas the latter rotates on its axis between said arms. 4. A device for knurling the thrust faces of the skirt portion of a piston of slightly oval shape, comprising a base, a work support on said base for holding a piston thereabove during knurling and for stabilizing the piston during rotation thereof on its axis, knurling mechanism slidably mounted relative to said base for movement away from and toward said work support longitudinally of the piston and comprising a pair of members adapted to clamp the wall of the piston therebetween with one of said members being rotatable to rotate the skirt of the piston therebetween, said work support comprising an upright post at one end of said base, a pair of upper and lower stabilizing arms mounted for vertical adjustment on said post and extending outwardly therefrom for receiving the head end of the piston diametrically therebetween, one of said arms being mounted for limited pivotal movement relative to said post whereby to accommodate the varying diameter due to the oval shape of the piston as the latter rotates on its axis between said arms, and spring means for yieldingly urging said one arm into contact with the piston.

5. A device for knurling the thrust faces of the skirt portion of a piston of slightly oval shape, comprising a base, a work support on said base for holding a piston thereabove during knurling and for stabilizing the piston during rotation thereof on its axis, knurling mechanism slidably mounted relative to said base for movement away from and toward said work support longitudinally of the piston and comprising a pair of members adapted to clamp the wall of the piston therebetween with one of said members being rotatable to rotate the skirt of the piston therebetween, said work support comprising an upright post at one end of said base, a pair of upper and lower stabilizing arms mounted for vertical adjustment on said post and extending outwardly therefrom for receiving the head end of the piston diametrically therebetween, said upper arm being secured to said post by means including a pair of pivot members whereby said upper arm is mounted for limited pivotal movement relative to said post for accommodating the varying diameter due to the oval shape of the piston as the latter rotates on its axis between said arms, and a helical spring coaoting between the inner end of said upper arm and said post above said pivot members for yieldingly urging the outer end of said upper arm into contact with the piston.

6. A device for knurling the thrust faces of the skirt portion of a piston of slightly oval shape, comprising a base, a work support on said base for holding a piston thereabove during knurling and for stabilizing the piston during rotation thereof on its axis, knurling mechanism slidably mounted relative to said base for movement away from and toward said work support longitudinally of the piston and comprising a pair of members adapted to clamp the wall of the piston therebetween with one of said members being rotatable to rotate the skirt of the piston therebetween, said work support comprising an upright-post atone end of said base, a pair of upper and lower stabilizing arms mounted for vertical adjustment on said post and extending outwardly therefrom for receiving the head end of the piston diametrically therebetween, one of said arms being mounted for limited pivotal movement relative to said post whereby to accommodate the varying diameter due to the oval shape of the piston as the latter. rotates on its axis between said arms, and a retaining member projecting from one of said arms and adapted to be received within a ring groove of the piston for preventing endwise 'movement of the latter during knurling.

7. A knurling means for a device for knurling the thrust faces of the skirt portion of a piston,=

movement longitudinally of the piston, a knurl ing roller rigidly supported in elevated position above said carriage at one end thereof and adapted to be positioned in engagement with the exterior surface of the skirt, driving means operatively connected with said knurling roller for effecti'ng relative rolling movement between said roller and the skirt circumferentially of the latter, a pivot shaft journaled on said carriage and x-tending longitudinally thereof, an upright bracket carried on said pivot shaft at the opposite end of said carriage, an elongated anvilsupporti-ng arm extending from said bracket longitudinally of said carriage and carrying an anvil-member at the outer end thereof for engaging the interior of the skirt substantially in alignment with the knurling roller radially of the piston, an upright lever (in said pivot shaft, and spring means operatively engaging said lever for yieldingly urging saida'nvil member toward said knurung rouer. v

eqxnurung means for a device for knurling the thrust faces of the skirt portion of a piston, comprising a carriage slidably mounted for movement longitudinally of the piston, a knurling member in the form of a roller rigidly supported in elevated position above said carriage at one end thereof and adapted to be positioned in engagenient with the exterior surface of the skirt, driving means operatively connected with said knurling roller for effecting relative rolling movement between said roller and the skirt circumferentially of the latter, a pivot shaft journaled on said carriage and extending longitudinally thereof, an upright bracket carried on said pivot shaft at the opposite end of said carriage, an elongated anvil-supporting arm extendin from said bracket longitudinally of said carriage and carrying an anvil member at the outer end thereof for engaging the interior of the skirt substantially in alignment with the knurlingroller radially of the piston, an upright lever on said pivot shaft, and spring means coacting with said lever for yieldingly urging said anvil member toward said knurling member, said spring means including tension adjusting means for varying the pressure between said members and manually operable releasing means for actuating said lever in the opposite direction against the spring action without substantially altering the tension of said spring means whereby to release the spring pressure urging the anvil member toward the knurling member and thereby permit disengagement of said members from the surfaces of the skirt.

9. Knurling means for a device for knurling the thrust faces of the skirt portion of a piston, comprising a carriage slidably mounted for movement longitudinally of the piston, an upright knurl support rigidly secured to said carriage at one end thereof, a knurling roller journaled at the upper end of said knurl support and adapted to be positioned in engagement with the exterior surface of the skirt, driving means operatively connected with said knurling roller for effecting relative rolling movement between said roller and the skirt circumferentially of the latter, a pivot shaft journaled on said carriage and extending longitudinally thereof, an upright bracket carried on said pivot shaft at the opposite end of said carriage, an elongated anvil-supporting arm extending from said bracket longitudinally of said carriage and carrying an anvil member at the outer end thereof for engaging the interior of the skirt substantially in alignment with the knurling roller radially of the piston, an upright lever on said pivot shaft adjacent said knurl sup? sort, and spring means coasting" with said knurl the thrust faces of the skirt portion of a piston, comprising a carriage slidably mounted for move-'- meht longitudinally or the piston, an uprightknurl support secured on said carriage at one end thereof, a knurling roller journaled at the upper end of said-knurl support and adapted to engage the exterior surface of the skirt, driving means s'peratively connected with said knurlingroller fer effecting relative rolling movement between said roller and the skirt circu'mferen tially of the latter, a pivot shaft journaled on said carriage extending longitudinally t ere of, an anvil member adapted to engage the inte rior of the skirt substai itially in alignment with the knurling roller radially of the piston, sup-'- porting structure-for said anvil member carrie on said pivot shaft at the opposite end ofsaid carriage for movement of said anvil member "away from and toward said knurling roller upon rock ing movement of said pivot shaft, an upright level" on said pivot shaft adjacent said knurl support, and adjustable spring loading means operatively associated with said supporting structure for yieldingly urging said anvil member toward said knurling roller whereby said roller and said anvil member-are pressed against the respective sur= faces of the skirt under a predetermined sub= stantially constant pressure, said spring loading means comprising an elongated member extending transversely through said knurl support adjacent the upper end of said lever, a helical spring carried concentrically on said elongated member for urging said lever in a direction to move said anvil member toward said knurling roller, means cooperating with said elongated member for adjusting the tension of said spring, and means on said elongated member for operatively engaging said lever for urging the same in the opposite direction against the action of said spring whereby to swing said anvil member away from said knurling roller without substantially altering the tension of said spring.

11. Knurling means for a device for knurling the thrust faces of the skirt portion of a piston, comprising a carriage slidably mounted for movement longitudinally of the piston, an upright knurl support rigidly mounted on said carriage at one end thereof and having an enlarged bore extending transversely therethrough, a knurling roller journaled at the upper end of said knurl support and adapted to be positioned in engagement with the exterior surface of the skirt, driving means for effecting relative rolling movement between said knurling roller and the skirt circumferentially of the latter, a pivot shaft journaled on said carriage and extending longit-udinally thereof, an anvil member adapted to engage the interior of the skirt substantially in alignment with the knurling roller radially of the piston, supporting structure for said anvil member carried on said pivot shaft adjacent the opposite end of said carriage for movement of said anvil member away from and toward said knurling roller upon rocking movement of said pivot shaft, an upright lever having a bifurcatedupper end mounted at the opposite end of said pivot shaft adjacent said knurl support, a swivel journaled in said knurl support and extending transversely of said bore, a second swivel journaled between the bifurcated portions of said lever,and a spring loading device coacting with said swivels and extending through said bore and said bifurcated end for urging said anvil member toward said knurling roller, said device including manual means for shifting said anvil member-into and out of coasting relation with said knurling roller by pivotal movement of said lever, and said here and the bifurcated upper end of said lever providing sufficient clearance to permit pivotal movement of said device upon pivotal movement of said lever.

12. A device for knurling the thrust faces of the skirt portion of a piston, comprising 'a knurl support, a knurling roller journaled at one end of said knurl support and adapted to engage the exterior surface of the skirt, an anvil member adapted to engage the interior of the skirt, supporting structure for said anvil member mounted in pivotal relation to said knurl support for movement of said anvil member away from and toward said knurling roller, an actuating lever operatively associated with said supporting structure for elTecting pivotal movement thereof, a swivel journaled in said knurl support, a second swivel journaled in said lever, an elongated member threaded transversely through said firstnamed swivel and extending transversely through said second-named swivel in slidable relation therewith, a helical spring encircling said elongated member at one end thereof adjacent said second-named swivel, said second-named swivel being operatively engaged at one side thereof with said spring for urging said lever toward said:

knurl support and urging said anvil member toward said knurling roller, said elongated member having a shoulder portion at the opposite side of said second-named swivel for engaging the latter whereby to urge said lever in the opposite direction against the action of said spring, and manually operable means for rotating said elongated member at its threaded connection with said first-named swivel for moving said shoulder portion into and out of engagement with said second-named swivel.

CERNYW F. JONES.

References Cited in the file of this patent UNITED STATES PATENTS 

